Piston for internal combustion engine



June 28, 1966 B. 1.. SHEAFFER 3,257,997

PISTON FOR INTERNAL COMBUSTION ENGINE Filed Feb. 4, 1965 INVEN TOR.

WHANN a McMAN/GAL Afforneys fbr A ab cam 1 Mum United States Patent Filed Feb. 4, 1965, Ser. No. 430,339 7 Claims. c1.123-73) This invention relates generally to internal combustion engines and relates more particularly to pistons for twocycle engines.

While the invention has particular utility in connection with pistons for two-cycle engines, and is shown and described in such connection, it is to be understood that its utility is not confined thereto.

As is well known, there are certain problems and difficulties involved in the provision of' suitable pistons for internal combustion engines. For example, there is the problem of eliminating or reducing to a minimum piston distortion due to internal strains and stresses set up by the rise in temperature resulting from the combustion of gases in the cylinder combustion chamber and it is an object of the present invention to provide a piston wherein the problems and difficulties involved therein are solved and overcome.

Another object of the invention is to provide a piston of this character that runs much cooler than prior pistons of which I am aware.

It is another object of the invention to provide a piston of this character that is relatively light in weight and wherein loads on the piston pin bosses will not distort the piston skirt.

Still another object of the invention is to provide a piston of this character wherein the piston pin wear is greatly extended, such wear having been found to be extended over 20%.

A further object of the invention is to provide a piston of this character that is very much lighter in weight than conventional pistons, thus correspondingly reducing inertia and problems resulting from high inertia factors and lowering reciprocating Weight.

A still further object of the invention is to provide a piston of this character that will work efficiently under all operating conditions.

Another object of the invention is to provide a piston of this character that is well balanced and has the required stability.

Still another object of the invention is to provide a piston of this character that is adapted to etficiently and effectively control transfer ports in the walls of cylinders of two-cycle engines.

The characteristics and advantages of the invention are further sufiiciently referred toin connection with the following detailed description of the accompanying drawings, which represent one embodiment. After considering this example, skilled persons will understand that many variations may be made without departing from the principles disclosed, and I contemplate the employment of any structures, arrangements, or modes of operation that are properly within the scope of the appended claims.

Referring to the drawings, which are for illustrative purposes only:

FIG. 1 is a longitudinal section through a two-cycle internal combustion engine having a piston embodying the present invention operably disposed therein, said piston being at the top of its stroke;

FIG. 2 is a sectional view taken on line 22 of FIG. 1;

FIG. 3 is a lower end view of the piston; and

FIG. 4 is a sectional view taken on line 4-4 of FIG. 2.

Referring more particularly to the drawings, there is ice diagrammatically shown a two-cycle internal combustion engine, indicated generally at 10, having a cylinder block 11, the upper part 12 of a crankcase indicated generally at 14, and the lower part 15 of the crankcase. The crankcase is of any suitable well known type and has an engine crankshaft 16 therein which includes a crank 17.

While the engine may be water cooled, it is shown as being of the air cooled type and the cylinder block is provided with a plurality of cooling fins 18 of the usual character and arrangement. There is a cylinder head 19 which is shown as being integral with the cylinder block but, it is to be understood, the cylinder head could be a separate part secured to the cylinder block by any suitable well known means and in any suitable well known man ner. The cylinder head is also provided with cooling fins 20 and there is a combustion chamber 21 in the inner side of said cylinder head.

A liner, indicated generally at 22, is cast in the cylinder block, said liner also being cast of suitable material, such as, for example, iron.

Liner 22 has a longitudinally extending interior bore 23 defined by a wall 24, said bore 23 being open at both ends.

An upper end portion of the liner wall 22 is provided with a plurality of external, annular ribs 25 spaced apart longitudinally or axially and when the liner is cast in the cylinder block said ribs securely anchor same in position in said cylinder block and against any longitudinal displacement. At one side the liner is provided with a boss 26 having at least one exhaust passage 27 which are in communication with the bore 24 of the liner by way of an exhaust port 28. The exhaust port is disposed at an intermediate position relative to the length of the liner and is adapted to be controlled by a piston, indicated generally at 30,.reciprocably mounted in the bore 24.

At the oposite side of the liner there is an external boss 31 having an inlet passage 32 'therethrough which communicates with the bore 2 3 of the liner by means of an inlet port 33. Inlet port 33 is positioned below the exhaust port 28, and said inlet port 33 is adapted to be controlled by said piston 30 and to be uncovered when the piston is in an upper range of movement.

At generally right angles to the bosses 26 and 31 for the exhaust and inlet passages, the liner is provided with diametrically arranged bosses or what may be termed blisters,each of which has a plurality of transfer passages or channels 35, 36 and 37, respectively. These passages are inclined upwardly and away from the side of the cylinder or bore 23 having the exhaust port 28, the upper ends of said passages being at substantially the same level and terminating in a horizontal plane below the plane of the top of said exhaust port 28. The lower ends of the passages or channels 35, 36 and 37, are shown as terminating upwardly of the lower end of the cylinder or bore 23, the lower ends of the passages 36 and 37 being lower than the lower end of the passage 35. While a plurality of transfer passages or channels are shown, it is to be understood that there may be only one or two or' more than three.-

The piston 30 has a flat topped head 40 and a depending skirt 41. Depending from and integral with the head 40 or" the piston are a pair of laterally spaced bosses 42 which have axially aligned openings 44 therethrough for reception of wrist pin bearings 45 in-which a wrist pin 46 is operably disposed. The upper end of a connecting rod, indicated generally at 48, is operably disposed on drical notch 49 therein for reception of a portion of the crank pin 17a of crank 17. There is also the usual clamp part 50 having a substantially semicylindrical notch for reception of the rest of the crank pin, 17a, said clamp part 50 being secured to the enlarged part of the connecting rod 48 in the usual manner by screws or bolts, not shown.

Piston 30 has a pair of openings 54 in the skirt in alignment with the openings in the bosses, said openings 54 being positioned at diametrical sides of the piston and in longitudinal alignment with said skirt openings 54 the skirt having arcuate relieved portions or notches 55 in the free end, said notches 55 being at diametrically opposite sides of the piston. Notches 55 are of the same size and character and openings 54 are also of the same size and character. This is done to keep the piston in balance and said notches and openings provide a piston of very light weight with the advantages of such light weight, as pointed out above.

Openings 54 in the piston also serve another purpose; that is, they serve as ports for the flow of fluid from the crankcase to the transfer passages or channels 35, 36 and 37, as will be described hereinafter.

The general sequence of engine operation Assuming that the engine is in operation and starting the description of such operation with the piston at lower dead center, the openings 54 in the piston skirt will be in communication with the transfer passages or channels 35, 36 and 37. A fuel mixture has been drawn into the crankcase interior 56 and compressed therein by the downstroke movement of the piston. At this time the inlet port 33 is, of course, closed by that portion of the piston skirt between the openings 54 at the right hand side thereof, as seen in the drawing, and the exhaust port 28 is uncovered and open.

For the first 45 to 70 of crankcase rotation from bottom dead center the transfer or scavenging channels 35, 36 and 37 are open so that the fuel mixture charge in the crankcase may flow therefrom through the openings 54, passages 35, 36 and 37, and into the cylinder above the piston. For the first 60 to 90 of crankshaft rotation from the bottom dead center the exhaust ports are open to! facilitate scavenging flow of combustion products therefrom. As the piston moves upwardly it begins to cover the exhaust pont 28 and the upper ends of the transfer passages 35, 36 and 37. When the piston head or the top of the piston reaches the upper edges of the transfer passages 35, 36 and 37, said passages are closed against the flow of fuel mixture upwardly into the upper portion of the cylinder 23. This occurs before the upper end of the piston reaches the upper edge of the exhaust port 28, so that the exhaust port remains open for a longer period than the transfer passages. When the upper end of the piston reaches the upper edge of the exhaust port the latter is fully closed and the fuel mixture charge in the cylinder above the piston is compressed with further upward movement of the piston.

As the piston moves upwardly from this position the fuel mixture is compressed in the upper part of the cylinder above the piston and in the combustion chamber 21. At the same time the skirt of the piston begins to uncover the inlet port 33 which is connected with the carburetor or other charge forming device, not shown. The upward movement of the piston has created a partial vacuum in the crankcase and as soon as the piston skirt begins to uncover the inlet port 33 a fresh charge of fuel mixture egins to be drawn through said inlet port 33, and thence into the bore or cylinder 23 and into the crankcase interior 56 with which the piston below its head 40 is in full communication.

When the piston has reached upper dead center, as shown in FIG. 1, and the fuel mixture in the upper end of the cylinder and combustion chamber 21 has been fully compressed, it is then ignited by a spark plug, not shown.

Upon ignition of this fuel mixture in the combustion chamber the piston is driven downwardly in its power stroke. As the piston moves downwardly it first reaches the upper edge of the exhaust port 28 and begins to uncover said port so that the exhaust gases or combustion products begin to escape through saidport. At the same time the piston has closed the inlet port 33 and begun to compress the fresh fuel mixture charge in the crankcase interior 56.

Upon further downward movement of the piston the upper ends of transfer passages 35, 36 and 37 are uncovered and since the openings 54 in the piston skirt communicate with said transfer passages the fuel mixture being compressed in the crankcase flow through said openings 54 and into the transfer passages 35, 36 and 37 and thence upwardly into the upper part of the cylinder. Because of the inclination of the transfer passages 35, 36 and 37 away from the side of the cylinder having the exhaust port, the fresh charge of fuel or the fuel mixture flows upwardly in the upper part of the cylinder toward the side away from the exhaust port and circulates so as to clear out or scavenge the combustion products in the upper end of the cylinder and the combustion chamber 21 and drive such combustion products downwardly along the side of the piston having the exhaust port and thence out of said exhaust port.

When the piston reaches lower dead center it begins its upward movement or stroke and the cycle of operation described above is repeated.

The invention and its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts of the invention without departing from the spirit and scope thereof or sacrificing its material advantages, the arrangement hereinbefore described being merely by way of example, and I do not wish to be restricted to the specific form or uses mentioned except as defined in the accompanying claims, wherein various parts or portions have been separated for clarity of reading and not for emphasis.

I claim:

1. In a piston for an internal combustion engine:

(A) a piston head;

(B) means for operable connection of a connecting rod to said piston;

(C) and a generally cylindrical skirt depending from said head, said skirt having oppositely arranged openings therein, said skirt having notches at opposite sides and in parallel alignment with the openings in said skirt, means connecting said rod with said piston comprising a pair of laterally spaced bosses integral with said head and depending therefrom, the outer sides of said bosses being spaced inwardly from the plane of inside configuration of the skirt, said bosses having aligned openings therein which are also aligned with the openings in the skirt, and a wrist pin in said bosses with its ends in spaced relation to the inner surface of the skirt.

2. In an internal combustion engine, including:

(A) wall means defining a cylinder having a piston receiving bore open at the inner end, said cylinder having (a) at least one exhaust passage therein communicating with the piston receiving bore by means of an exhaust port,

(b) an inlet passage communicating with said piston receiving bore by means of an inlet port spaced closer to the inner end of said cylinder than said exhaust port,

(c) at least one blister positioned at an angle to said ports,

(d) at least one transfer passage in said blister for the flow of fuel and oil into the cylinder bore, the inner end'of said passage terminating short of the inner end of the cylinder;

(B) and a piston reciprocably disposed in the piston receiving bore of the cylinder, said piston including (a) a piston head,

(b) means for operably connecting said piston with an engine connecting rod,

(c) and a generally cylindrical skirt depending from said piston head, said skirt having at least one opening therein adapted for communication With the transfer passage while the piston is within a predetermined range of movement in the bore of the cylinder so that fuel and oil may fioW through said opening, about the means for operably connecting said piston with an engine connecting rod, into said transfer passage, and thence into the cylinder bore outwardly of the piston,

the means connecting said rod to said piston including a a pair of laterally spaced bosses depending from said piston head and a wrist pin in said bosses with its ends in spaced relation to the inner surface of said skirt, said bosses having aligned openings therein which are also aligned with the openings in the skirt, said bosses being spaced inwardly from the plane of inside configuration of the skirt, the free end of said skirt having notches in parallel alignment with respective openings in said skirt.

3; In an inernal combustion engine, including:

(A) wall means defining a cylinder having a piston receiving bore open at the inner end, said cylinder having (a) at least one exhaust passage therein communicating with the piston receiving bore by means of an exhaust port,

(b) an inlet passage communicating with said piston receiving bore by means of an inlet port spaced closer to the inner end of said cylinder than said exhaust port,

(c) at least one blister positioned at an angle to said ports,

(d) at least one transfer passage in said blister for the flow of fuel and oil into the cylinder bore, the inner end of said passage terminating short of the inner end of the cylinder;

(B) and a piston reciprocably disposed in the piston receiving bore of the cylinder, said piston including (a) a piston head,

(b) means for operably connecting said piston with an engine connecting rod,

(c) and a generally cylindrical skirt depending from said piston head, said skirt having at least one opening therein adapted for communication with the transfer passage while the piston is within a predetermined range of movement in the bore of the cylinder so that fuel and oil may flow through said opening, about the means for operably connecting said piston with an engine connecting rod, into said transfer passage, and thence into the cylinder bore outwardly of the piston,

(d) a crankshaft having a crank pin,

(e) means supporting said crankshaft in operable relation to the piston receiving bore of the cylinder,

(f) and a connecting rod, one end of said connecting rod having an operable connecting with the crank pin of said crankshaft, the other end of the connecting rod having the operable connection with the piston,

the free end of the skirt having notches therein in parallel alignment with the respective openings in said skirt, the means connecting said rod to said piston comprising a pair of laterally spaced bosses depending from the head of the piston, said bosses having aligned openings therein which are also aligned with the openings in the skirt, the adjacent end of the connecting rod also having an opening therein aligned with the openings in said bosses; and a Wrist pin disposed in said aligned openings in the bosses and connecting rod, and said bosses being spaced inwardly from the plane of the inside configuration of the skirt.

4. In a two-cycle internal combustion engine assembly:

(A) a cast iron cylinder liner having a longitudinally extending cylindrical bore therethrough open at both ends, said cylinder liner having (a) a plurality of annular, longitudinally spaced external ribs on an upper end portion,

(b) a boss at one side having an exhaust passage therein communicating with the bore of said liner by means of a port,

(c) said exhaust port being located intermediate the ends of the liner and intermediate the ends of the stroke of a piston reciprocably mounted in said bore,

((1) a second boss having an inlet passage therethrough communicating with the cylindrical bore of the liner by means of an inlet port,

(e) said inlet port being spaced closer to the inner end of the liner than said exhaust port,

(f) a pair of blisters at right angles to the exhaust and inlet bosses and arranged diametrically opposite to each other, each of said blisters having a plurality of passages formed therein opening into said cylindrical bore and extending toward the outer end of said liner and inclined away from the side having the exhaust port, the upper ends of said transfer passages in said blisters having their upper ends terminating longitudinally inwardly of the outer edge of the exhaust port;

(B) a cylinder block cast about said liner and leaving the outer ends of the inlet passage and the exhaust passage free;

(C) and a piston for reciprooable motion within the bore of the liner, said piston having a head and a generally cylindrical skirt, the latter having oppositely arranged openings therein adapted to be in communication with the transfer passages, said skirt having notches at opposite sides and in parallel alignment with the openings in said skirt, and means connecting a connecting rod with said piston comprising a pair of laterally spaced bosses integral with said head and depending therefrom, the outer sides of said bosses being spaced inwardly from the plane of the inside configuration of the skirt, and said bosses having aligned openings therein which are also aligned with the openings in the skirt and a wrist pin in said bosses with its ends in spaced relation to the inner surface of the skirt whereby fluid from the crankcase of the engine may pass into the piston, through said openings in the skirt thereof, thence into the transfer passages and into the upper end of the bore of the liner, said inlet port, exhaust port and transfer passages being controlled by the piston. 5. In a two-cycle internal combustion engine assembly: (A) a cylinder liner having a longitudinally extending cylindrical bore therethrough open at both ends, said cylinder liner having (a) a boss at one side having an exhaust passage therein communicating with the interior bore of said liner by means of an exhaust port,

(b) said exhaust'port being located intermediate the ends of the liner and intermediate the ends the stroke of a piston reciprocably mounted in said bore,

(c) a second boss having an inlet passage therethrough communicating with the cylindrical bore of the liner by means of an inlet port,

(d) said inlet port being spaced closer to the inner end of the liner than said exhaust port,

(e) at least one blister at substantially right angles angles to the exhaust and inlet bosses, said blister having a plurality of passages formed therein having at least a portion of their length opening into said bore and extending toward the outer end of said liner and inclined away from the side having the exhaust port, the upper ends of said transfer passages in said blister having their upper ends terminating inwardly of the 7. In an internal combustion engine; wall means defining a cylinder having a piston receiving bore extending longitudinally therein, said cylinder having (a) at least one exhaust passage therein communicating with the piston receiving bore by means of an exhaust port,

(b) an inlet passage communicating with said piston outer edge of the exhaust port; 1 (B) a cylinder block cast about said liner and leaving the outer ends of the inlet passage and the exhaust passage free; V (C) and a piston for reciprocable motion within the bore of the liner, said piston having ahead and a generally cylindrical skirt, the latter having oppositely arranged openings therein adapted to be in communication with the transfer passages, said skirt having notches at Opposite sides and in parallel alignreceiving bore by means of an inlet port, said inlet port being spaced closer to the inner end of said cylinder than said exhaust port,

ment with the openings in said skirt, and means conat least One blister Positioned at an angle to a d necting a connecting rod with said piston compris- Ports, a plurality of generally Parallel transfer P ing apair of laterally spaced bosses integral with said Sages in Said hllstel', Said Passages being inellnecl head and depending therefrom, the outer sides of toward the Outer end of the here y from the said bosses being spaced inwardly from the plane of Port, the transfer Passage adlatent the exhaust the inside configuration of the skirt, and said bosses P 'helng Shorter than the other P g the Outer having aligned penings th i hi h are l ends of said transfer passages terminating in. subaligned with the openings in the skirt and a wrist pin Stahtlally the m Plane normal to the aXlS of the in said bosses with its ends in spaced relation to the Cylinder, the inner ends of Said Passages terfnlnatlng inner Surface f t Shift whereby fluid fromthe short of the inner end of the cylinder with the shorter crankcase of the engine may pass i t h piston, passages having their inner ends spaced further outthrough said opening in the skirt thereof, thence into Wardly longitudinally 0f the Cylinder than the inner the transfer passages and into the upper end of the e of the longer P a Second nP bore of the liner, said inlet port exhaust port and honed diametrically PPP e first Inentlened transfer passages b i t ll d b h piston blister, said second blister also having a plurahty of 6. In a two-cycle internal combustion engine assembly: generally P l transfer pflssagesfhereln l the (A) a cast iron cylinder liner having a longitudinally ph e 1n Bald Seeeml t g substantlally extending cylindrical b r th i id li d liner similar to the passages n said first blister, a p1ston having in said cylinder, said piston having a head and a (a) an exhaust ort communicating wi h generally cylindrical skirt depending therefrom, said terior bore of said liner, skirt having openings therein at diametrically op- (b) said exhaust port being located intermediate PQ Sides nd at the sldes having said blisters,

the ends of the stroke of a piston reciprocably sald P h helhg S0 dlmehelohed as to be In h mounted in aid bor municatron wrth some of sa d passages at various an i l port communicating with the cylim piston posrtlons, said sk rt having notches at opposite drical bore f th li SlClCS and in parallel ahgnmentwith the openings in (d) said i let t b i spaced closer to the inner sa d sk rt, and means connecting a connecting rod end of the li h id exhaust port, with sa d piston compr sing a pair of laterally spaced (e) at least one blister spaced circumferentially bosses Integral h heafl and depenflmg there from said exhaust port approximately 90, said the outer sldes of Sald p bemg f bli ter having at least one passage f d there inwardly from the plane of the lnside configurahon in extending toward the outer end of said liner of e t, d sald bosses having aligned o enin s and inclined away from the exhaust port, said there]? Whlch Wlth the m g a transfer passage b i open along at least a pop the skirt and a wr1st pin in said bosses with 1ts ends ti f h inner id and having its upper end 5 in spaced relation to the inner surface of the skirt.

r a 0 i d i zl ti st ggrt g of the outer edge of the References Cited by the Examiner (B) a cylinder block cast about said liner; UN S A PATENTS (C) and a piston for reciprocable motion within the 961 315 6/1910 Peugeot et a1. 123 73 bore of the liner, said p1ston having a head and a 1051977 2/1913 Wood 123 73 g ally ylindrical skirt, the latter having oppositely arranged openings therein adapted to be in commu- FOREIGN PATENTS nication with the transfer passage, said skirt having 408,243 1/1909 France. notches at opposite sides and in parallel alignment 1,081,882 6/1954 France w1th the openings in said Skllt and means connectin g 1,201,692 7/1959 France a connecting rod with said p1ston comprising a pair 737,045 7/1943 Germany of laterally spaced bosses-integral with said head and depending therefrom, the outer sides of said bosses being spaced inwardly 'from the plane of the inside configuration of the skirt, and said bosses having CARLTON R. CROYLE, Primary Examiner.

WENDELL E. BURNS, Examiner, 

2. IN AN INTERNAL COMBUSTION ENGINE, INCLUDING: (A) WALL MEANS DEFINING A CYLINDER HAVING A PISTON RECEIVING BORE OPEN AT THE INNER END, SAID CYLINDER HAVING (A) AT LEAST ONE EXHAUST PASSAGE THEREIN COMMUNICATING WITH THE PISTON RECEIVING BORE BY MEANS OF AN EXHAUST PORT, (B) AN INLET PASSAGE COMMUNICATING WITH SAID PISTON RECEIVING BORE BY MEANS OF AN INLET PORT SPACED CLOSER TO THE INNER END OF SAID CYLINDER THAN SAID EXHAUST PORT, (C) AT LEAST ONE BLISTER POSITIONED AT AN ANGLE TO SAID PORTS, (D) AT LEAST ONE TRANSFER PASSAGE IN SAID BLISTER FOR THE FLOW OF FUEL AND OIL INTO THE CYLINDER BORE, THE INNER END OF SAID PASSAGE TERMINATING SHORT OF THE INNER END OF THE CYLINDER; (B) AND A PISTON RECIPROCABLY DISPOSED IN THE PISTON RECEIVING BORE OF THE CYLINDER, SAID PISTON INCLUDING (A) A PISTON HEAD, (B) MEANS FOR OPERABLY CONNECTING SAID PISTON WITH AN ENGINE CONNECTING ROD, (C) AND A GENERALLY CYLINDRICAL SKIRT DEPENDING FROM SAID PISTON HEAD, SAID SKIRT HAVING AT LEAST ONE OPENING THEREIN ADAPTED FOR COMMUNICATION WITH THE TRANSFER PASSAGE WHILE THE PISTON IS WITHIN A PREDETERMINED RANGE OF MOVEMENT IN THE BORE OF THE CYLINDER SO THAT FUEL AND OIL MAY FLOW THROUGH SAID OPENING, ABOUT THE MEANS FOR OPERABLY CONNECTING SAID PISTON WITH AN ENGINE CONNECTING ROD, INTO SAID TRANSFER PASSAGE, AND THENCE INTO THE CYLINDER BORE OUTWARDLY OF THE PISTON, THE MEANS CONNECTING SAID ROD TO SAID PISTON INCLUDING A PAIR OF LATERALLY SPACED BOSSES DEPENDING FROM SAID PISTON HEAD AND A WRIST PIN IN SAID BOSSES WITH ITS ENDS IN SPACED RELATION ALIGNED OPENINGS THEREIN WHICH ARE ALSO BOSSES HAVING ALIGNED OPENINGS THEREIN WHICH ARE ALSO ALIGNED WITH THE OPENINGS IN THE SKIRT, SAID BOSSES BEING SPACED INWARDLY FROM THE PLANE OF INSIDE CONFIGURATION OF THE SKIRT, THE FREE END OF SAID SKIRT HAVING NOTCHES IN PARALLEL ALIGNMENT WITH RESPECTIVE OPENINGS IN SAID SKIRT. 